歸并排序Java實作

public class MergeSort {

    public static void sort(int[] a, int low, int high) {
        if (low >= high)
            return;
        int mid = (low + high) / 2;
        sort(a, low, mid);
        sort(a, mid+1, high);
        merge(a, low, high, mid);
    }

    public static void merge(int[] a, int low, int high, int mid) {
        if (low >= high)
            return;
        int[] tmp = new int[high - low + 1];
        int l = low;
        int r = mid+1;
        int i = 0;
        while (l <= mid && r <= high) {
            if (a[l] < a[r]) {
                tmp[i] = a[l];
                l++;
            }else {
                tmp[i] = a[r];
                r++;
            }
            i++;
        }
        while (l <= mid) {//左邊還有，全部加入
            tmp[i] = a[l];
            l++;
            i++;
        }
        while (r <= high) {//右邊還有全部加入
            tmp[i] = a[r];
            r++;
            i++;
        }
        for (int j = 0; j < tmp.length; j++) {
            a[low + j] = tmp[j];
        }
    }



    public static void main(String[] args) {
        int[] arr = {22,5,3,3,4,9,2,8,3,0,1,5,6,11};
        sort(arr, 0, arr.length - 1);
        System.out.println(Arrays.toString(arr));
    }
}